The air conditioning in my xg350 is on full blast and wont go off, even if i push the off button.

This is due to the fact that the solenoid relay is stuck and so the ac is not cutting off. You need to open the hood and check after starting the car. If the fan is cut , does the ac cut off, if not the relay or the solenoid of the compressor must be checked.

Change the relay located on the backside of the fuse box on the drivers side.

does heater work on low settings

Low coolant is detected by a sensor inside the plastic resevoir tank. These things lie, so if the resevoir has plenty of coolant, it's probably a dirty or faulty sensor. If you can't see coolant, add it directly to the resevoir. As for the A/C, you can purchase an A/C pressure gauge or complete check and fill kit at a parts store and follow the directions for using it. If the pressure reads low, with the car running and A/C on full blast, add refrigerant until you hear the compressor turn on. Check your gauge again. Once you have it to pressure, you should be good to go. If it never gets there, you have problems. If it gets there and stops working again days later, you have a slow leak.

The control head is bad

Your blower motor resistor needs to be replaced. when they go bad, for some reason the fan will only work on high. Replace that resistor and you will be good to go. Let me know if you have any further questions. Thanks for using FixYa!

check were the blower is at that panel were the air runs thru it gets full of dirt you might want to clean it out that will help.

there's a bad switch somehwere inside the dash. What does the dealer say?

replace fuse and relay for air conditioer.

Same thing I have a 2003 9-3 with manual controls and the fan suddenly won't shut off. Through my investigation it is the "Fan Control Resistor Module". See saabcentral.com forums. The part number is 90512510 and it will cost around 250 bucks to DIY.

Good Luck.